Orangutans sacrifice sleep to socialize–but naps can help
If you’ve already spent a late evening with friends and needed an overview of the afternoon the next day, you are in good primate. Wild orangs-our ways also take a nap to compensate for the lost sleep, according to new research on a population of Orangs-Outan in Indonesia. And, one of the largest factors determining the amount of sleep they obtain is their social environment, according to the study published on June 25 in the journal Current biology.
Orangutans are considered to be large semi -solitic apes, which means that they have their own individual ranges and – with the exception of mothers and infants – spend a lot of their days alone. However, they always interact socially, voluntarily spending more than half of their time near others, according to sex and the stage of life. Unlike humans, who have evolved in hunter groups, orangutans come from a more lonely line. Socialization always seems really important for monkeys, as the new conclusions pointed out. When orangutans choose to spend the night near the others, they rest less and make more naps the next day, report scientists. However, despite lost sleep, orangutans often choose to build their night nests near each other.
“They really seem to have control over who they spend time,” said Caroline Schuppli, co-author of the study and evolutionary biologist and research group manager at the Max Planck Institute of Animal Behavior in Konstanz, Germany, Popular science. “If they really needed a night for themselves, they could make sure they got it. For me, the result shows how vital social associations are, even for this semi-solitary species. … This is not something that they can simply give up because they sleep less.”
The new research also reveals other surprising parallels between human and orangutan sleep habits. The length of naps, the influence of temperature and travel, and even a pre-sum of bed routine among the orangutans reflect all our own trends-adding to the ever-increasing list of lines shared between us and our orange fur cousins.
“We can learn a lot about the evolutionary history of sleep by studying it in the parameters in which it has evolved,” explains Schuppli.
Rakus, a bridle male, ends his night nest and then rests there. Credit: Suaq Project & Foundation.
Orangutans “make their beds”
Between 2007 and 2023, Schuppli and a team of local assistants in Indonesia spent hundreds of days and nights after individual oranguts from their awakenings early in the morning until their evening bed hours and beyond. To ensure in-depth follow-up, three people were assigned to monitor each orangutan. Armed with binoculars and with the neck collided at the Trees peak while walking the swampy forest of peat in Sumatra, the team collected data on 53 adult people over the 17 years.
Each evening, before turning around for the night, the orangutans “make their beds”, building leafy nests of twigs and foliage on which to rest. Researchers observed that this particular population of Orangs-Outans also built slightly simpler nests for daytime naps, unlike other groups which are often found on naked branches.
To approximate the sleep time, scientists have recorded how long each individual spent quietly lying in these nests in each case. On average, every night, the Orangs-Outans entered their nests around 5:40 p.m., less than an hour before sunset, and left them just after sunrise around 6:28 am, passing a little less than 13 hours “in bed”.
At least one study on captivity orangutans has previously shown that primates spend about 75% of their quiet time in their sleep nests, therefore 13 hours of nest time amount to less than 10 hours of estimated night sleep. The monkeys also spent an average of 76 minutes to take a nap every day, more than 1-2 different nests and several episodes of rest. The average nap duration was approximately 10 minutes.
“It is surprisingly similar to what is recommended in humans for the duration of a nap,” explains Schuppli.
Beyond these basic sleep statistics, scientists also compromised how the duration of a rest at rest influences the following, on the basis of the many cases where they were able to follow the same orangutans through two days or more. They also compared the time spent in nests with environmental and social variables such as temperature, precipitation, proximity to other orangutans, the duration of daily trips and the amount of food consumed.
They discovered that orangutans do not seem to compensate for a shortened night with more rest the next night. Instead, they compensate for naps. For each hour of lost night nest rest, the monkeys showed an increase of 12.3% (approximately 10 minutes) in their quantity of diurnal drowsiness. “There is a kind of NAP quota that they may try to make,” says Schuppli.
The population of Orangs -Outans followed in the study is unique in its use of routine and its level of sociality – the two things that require a lot of cognitive energy. So sleeping enough in this group, she adds.
[ Related: These orangutans indulge in a spa-like skincare routine. ]
Lose sleep, make friends
Many scientists have observed orangutans and other primates over the years, following and meticulously recording their daytime activity. But this new research proves that the understanding of the night inactivity Can also enlighten our understanding of our nearest parents on the tree of life. “It’s cool to start digging in the almost half of their lives they were sleeping,” said Alison Ashbury, main study author and also an evolutionary biologist at the Max Planck Institute Popular science. “All this question of sleep in wild animals becomes a more important research subject, because we get more technology and we are really [examine it]”, She said.
Among all the variables examined, the greatest unique determinant of the duration of an individual in his nest every night was the presence or absence of other orangutans. For all additional association partners and called nearby, a period of sleep of an orangutan was about 14 minutes shorter. The main driving factor here seemed to be a time of awakening. “They come out of their nests earlier when they are with others … As soon as the first leaves, everyone leaves,” she notes. Schuppli and his colleagues do not yet know why the Orangs-Outans choose to sacrifice the rest for social sleep, but this could be due to the fact that he strengthens the links during the hours of watch, as observed in a study in 2024 of the baboons.
The temperature also played an important role, with extreme rest periods. “As it cools at night, they sleep less, and as it is warmer during the day, they sleep less. So there is a kind of ideal scope for sleeping ”, just like in humans, explains Ashbury. In addition, the more an orangutan traveled during the day, the less they fall asleep, usually because of a later bedtime. Relatively, on rainy days, the monkeys took a nap more.
The study authors could not directly measure the Orangs-Outans, rather based on the nest time proxy. So, the exact sleep numbers may be different if the real repetition time was easily quantified, without disturbing wild primates. It is also likely that there were differences in the quality of the night and the depth of sleep that the researchers were not able to capture, as well as environmental variables beyond the scope of what they have evaluated.
However, overall, the results highlight how much sleep and socialization are critical for orangutans and how the environment can shape restful rest. What applies to other monkeys is best kept in mind for ourselves, says Schuppli.
“You shouldn’t be ashamed if you need a nap during the day.”
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